What single reagent solution (including `H_(2)O)` could be used to effect the separation of the following of solides?
a. `Ni(OH)_(2) and Fe(OH)_(2)`
b. `Cr_(2)O_(3) and Fe(OH)_(3)`

Explanation

a.`H_(2)O` can dissolve `NaOH_(2) ,Fe(OH)_(3)` remain insoluble in water .
b. `NH_(4)OH` dissolves `Ni(OH)_(2)` is insoluble `Ni(OH)_(4) + 4NH_(4) OH rarr underset("Soluble")underset("Soluble")([Ni(NH_(3))_(4)]^(2+))`
c. Execess of `NaOH` can dissoolve `Cr_(2)O_(3)` but `Fe(OH)_(3)` remain insoluble
`Cr_(2)O_(3) + 3H_(2)O rarr 2Cr(OH)_(3)`
`Cr(OH)_(3) + NaOH rarr underset("Soluble")(Na[Cr(OH)_(4)])`
d.Dilute `HCI` disolves `MnS` souble while `CoS` remain insoluble
`MnS + 2HCI rarr MnCI_(2) + H_(2)S uarr`
e. `Aq,NH_(3)` would dissolve `AgCI` while `AgI` remain insoluble
`AgCI + 2NH_(3)(aq) rarr underset("Soluble")([Ag(NH_(3))_(2)]CI)`